Tone compensated volume control



Feb. 4, 1936. 1.. F. CURTIS TONE COMPENSATED VOLUME CONTROL Filed Sept.11, 1934.

- INVENTOR [Ail/f [Cher/5 ATTORNEY Patented Feb. '4, 19 6 2,029,523.

UNITED STATES PATENT OFFICE y 2,029,523 TONE COMPENSATED VOLUME CONTROLLeslie F. Curtis, Springfield, Mass., assignor to United American BoschCorporation, Springfield, Mass., a corporation of New York ApplicationSeptember 11, 1934, Serial No. 243,534

' 9 Claims. (Cl. 179-1) This invention relates to a volume control forH3 in the cathode circuit, shunted by a bypass radio or alliedelectrical equipments, and more condenser M. particularly to a tonecompensated volume con- As earlier mentioned the human ear does nottrol. It is well known that the response of the have a flat response atlow volume levels, but

ear to the audio frequency band is not proporfavors the middleaudio'frequencies at the extional at different volume levels. The middlepense of the higher and lower frequencies. If frequencies have anapparent response greater an amplifier has a flat frequency response andthan that of the lower frequencies at the volume repr u music at theOriginal Studio Volume level of average home entertainment. To'comlevel, 110 Compensation is needed- The 11511811 10 pensate for thisnon-linear response, thelower home entertainment level is, however, butafrac- 10 frequencies should be reduced in less degree than tion of thestudio level and req bass the remaining frequencies in order to producean p at on to achieve netllrelism- With a Studio effect of realism atlow volume levels. level of 60 decibels at 1,000 cycles which is toTherefore one object of the invention is to be reproduced at a level 35decibels lower, a 100- provide a tone compensated volume control cycletone should be reduced only about 17 deci- 5 which reduces the middleand higher frequencies ,bels in order to compensa for the peculiaritiesproportionately more than the lower frequencies. of the ear, a d tPresent/eh effect of realism Hit A u ther object'is to provide acombined volthe lower level. The difierential between the ume and tonecontrol. necessary energy level of the IOU-cycle and the 20 Otherobjects and advantages will in part be IOOO-cycle tones varies accordingto the level of 20 stated and in part be apparent when thefollowreproduction as' contrasted with the original ing specification isread'in connection with the u ie le e T ci cu ShOWn in the drawingdrawing in which the figure'is a diagrammatic ay b adjusted toautomatically r u t t is representation of the volume control showing itdifie n al a e d g t0 the requirements of the applied to an audiocircuit. diiferent volume levels. In case the maximum 5.

Referring to the drawing more in detail, the output of the amplifierdoes not equal the studio numeral I represents a vacuum tube comprisinglevel, the resistance 6 is inserted into the circuit the first audiostage of an amplifier. The tube I and ha a value determin d by h diffrence has in the cathode circuit a biasing resistor 2 between theselevels. Thus in most home inwhich is shunted by a bypass condenser 3,The stallations some initial compensation is required 3 plate potentialis fed through a plate coupling v t ful V me of the amplifier- With fresistor 4, and a coupling condenser 5 transmits amplifier Volume equalto the Studio level, 0011- audio frequencies to the next amplifierstage. "denser Of and P f 500,000 Ohms, it A fixed resistance 6 isserially connected with the a e f u d that resistanqe 8 should v y p- 85resistance element R of a volume control popr ximat y nv s ly s h squarer t of the tentiometer'P, the other end of the resistance r a ce R" yibelow the potentiometer element being grounded. For the sake of claritych va at o is ubs a y t e a e a the resistance element R is divided intoa secthat in direct proportion to the Square root of tion -R' lyingabove the movable potentiometer the ratio between the original, and thereduced 40 arm I, and a sectionR" whichhes below the v m v l at 1000cycles. This may be ex- 40 potentiometer arm. A variable tone controlrepressed math m t a y as resistance va i a sistance B has an endconnected to the coupling 1 condenser 5 and the other end free.Resistance 8 has a slidable contact 9 which is connected to a tonecontrol condenser II) which may be varior resistance 8 varies as 45able, although the invention will operate successfully with a fixedcondenser. A common shaft 29 may control both the arm 1 and contact 9,but it is not essential to obtain the improved perwhere E0 is thegreatest available signal voltage formance of the invention. The otherside of and Eg is the voltage across the input of tube 50 condenser I0is connected to the potentiometer I2. If resistance 8 is fixed, the lowfrequencies arm I. The signal is taken from a point=beare quicklyreduced as the volume is initially tween condenser l0 and slidablecontact 9 and is lowered, and thereafter they remain constant, led tothe input circuit of tube l2 of the second independent of any furthervolume-level. This audio stage. Tube I! also has a biasing resistor hasbeen the case with prior controls. For re- 55 production in rooms ofdifferent acoustic properties, it may be desirable to have the basscompensation adjustable at will. This is readily accomplished by makingthe condenser III ndependently variable or adjustable, as shown in Fig.l. The resistance 8 under this condition is varied proportionally withthe potentiometer resistane R exactly as before.

It will be apparent that many changes and modifications may be made inthis invention by any one skilled in the art without departing from thescope and true spirit of the invention as defined in the followingclaims.

What is claimed is:

audio source, a potentiometer having a resistance connected across saidsource, a variable resistance connected in series with said source, aslider arm on said potentiometer, a movable contact on said variableresistance, a condenser connected between said slider arm and saidmovable contact, and an output connection between said condenser andsaid movable contact.

2. In a compensated volume control circuit, an audio source, a seriescircuit comprising a fixed resistance and a potentiometer resistanceconnected across said source, a variable resistance connected in serieswith said source, a slider arm on said potentiometer, a movable contacton said variable resistance, a condenser connected between said sliderarm and said movable contact, and an output connection between saidcondenser and said movable contact.

3. In a compensated volume control circuit, an audio source, apotentiometer having a resistance connected across said source, avariable resist-,

ance connected in series with said source, a slider arm on saidpotentiometer, a movable contact on said variable resistance, a variablecondenser connected between said slider arm and saidmovable contact, andan output connection between said condenser and said movable contact.

4. In a compensated volume control circuit, an audio source, a seriescircuit comprising a fixed resistance anda potentiometer resistanceconnected across said source, a variable resistance connected in serieswith said source, a slider arm .on said potentiometer, a movable contacton said variable resistance, a variable condenser connected between saidslider arm and said movable contact, and an output connection be-' tweensaid condenser and said movable contact.

5. In a compensated volume control circuit, an audio source, apotentiometer having a resistance connected across said source, avariable resistance connected in series with said source, a sliderarmarm on said potentiometer, a movable contact' on said variableresistance, a mechanical drive connection between said slider arm andsaid mov- 1. In a compensated volume control circuit, an...

able contact, a variable condenser electrically connected between saidslider arm and said movable contact, and an output connection betweensaid condenser and said movable contact.

'7. In a compensated volume control circuit, an audio source, a seriescircuit comprising a fixed resistance and a potentiometer'resistanceconnected across said source, a variable resistance connected in serieswith said source, a slider arm on said potentiometer, a movable contacton said variable resistance, a mechanical drive connection between saidslider arm and said movable contact, a condenser electrically connectedbetween said slider arm and saidmovable contact, and an outputconnection between said condenser and said movable contact.

8. In a compensated volume control circuit, an audio source, a seriescircuit comprising a fixed resistance and a potentiometer resistanceconnected across said source, a variable resistance connected in serieswith said source, a slider arm onsaid potentiometer, a movable contacton said variable resistance, a mechanical drive connection between saidslider arm and said movable contact, a variable condenser electricallyconnected between said slider arm and said movable contact, and anoutput connection between said condenser and said movable contact.

9. In a compensated volume control circuit, an audio source, apotentiometer-having a resistance connected across said source, avariable resistance connected in series with said source,'a slider armon said potentiometer, a movable contact on said variable resistance, amechanical drive connection between said slider arm and said movablecontact, a condenser electrically connected between said slider arm andsaid movable contact, and an output connection between said condenserand said movable contact, whereby said variable resistance increases assaid slider arm moves toward low volume position.

LESLIE F. CURTIS.

